Week 4: Modeling Odor Stimulation

With the entire Antennal Lobe in place, it’s time to add some stimulus! We are going to start with odor stimulus, which is encoded by olfactory receptor neurons and sent to the Antennal Lobe. To start, we will go over some of the requirements of our odor pulses.

 

For starters, odors are actually diffuse molecules in the air. These molecules excite specific olfactory receptor neurons, which then send signal to the Antennal Lobe. The variety of scents that we are able to perceive is a result of the combinatorial nature of this process. Each odor excites a subset of olfactory receptor neurons, and then each olfactory receptor neuron excites a subset of glomeruli within the Antennal Lobe. With so many possible subsets, its easy to see how we are able to have such a perceptive sense of smell.

 

To simplify our own model, we decided not to explicitly model the olfactory receptor neurons. Rather, when an odor pulse arrives, it modulates the background firing rate to simulate additional neuron firing from the olfactory receptor neurons. This method proved successful, so we have no need to over complicate our model by adding even more neurons.

 

To model the odor pulse itself, we required each odor pulse to have three distinct phases: the rising phase, the stimulus phase, and the decay phase. The rising phase occurs when the odor is first introduced. The stimulus sent to the Antennal Lobe is modeled by a sigmoidal curve in order to have the signal rise from nothing to its maximum odor signal. The next phase is the stimulus phase. During this phase, the odor stimulus remains at the max odor signal level. Finally, after the odor is over, we have the decay phase. During this phase, the odor signal decays away according to an exponential decay until it is back to where it started. All three phases of this odor pulse help to recreate some of the realistic dynamics observed by real olfactory receptor neurons. A graph of what the signal looks like during an odor pulse is shown below.

 

OdorPulseEquation

 

With an odor pulse in place, we now hope to further tune the Antennal Lobe and our odor pulses in order to observe the three distinct behaviors found in the Antennal Lobe as a result of odor stimulation. We will continue trying to create these dynamics next week.

 

Comments

  1. chelschive says:

    I’ve never heard of research into odors! As a neuroscience major, its really interesting to see all the types of research possible within the field. This sounds super interesting and I look forward to seeing your future week updates.

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